Compressor unloader



Nov. l2, 1935.

R. W. AYRES COMPRES S OR UNLOADER Filed June 14. 1954 'Trigg l.

Inventor; Russell W Agr'es,

ls Atto-#heg Patented Nov. 12,' 1.935

'i UNITED. STATES .PATENT oFricI-z A 'l f amsn f 'y Russell W. Anci;

Schenectady General Electric Company, a corporation of New York Application 1m 14, 1934, serial No. 'man .s claim. (ci. :so-13s) My invention relates to unloaders for fluid compressors, and more vparticularly to devices for unloading'V fluid compressors of the rotary type.

When an electric motor, such as the motors 5 commonlyemployed for driving the compressors of refrigerating machines, is started, it is desirable that the load connected thereto be as small `as possible, so that a minimum starting current shall be required. In order to accomplish this, it is necessary to provide some `means for preventing the loading of the compressor until the motor has attained sumcient speed torcarry the load without requiring excessive current. The

unloading of refrigerant compressors'is usually accomplished by some by-passing arrangement whereby the intake and exhaust portsare placed in communication, thus preventing the building up of arrv pressure by the compressor. When a rotary compressor is employed, it has heretoforel sure arrangement responsive to operation of the compressor for'forcing the blade out of its retracted positionY to load the compressor when a predetermined speed has been reached.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part'of this specification.

For a better understanding ofl my invention reference may be had to the accompanying drawing, in which Fig. 1 is a sectional elevational view of a, refrigerating machine provided with a compressor embodying my invention: Fig. 2 is an enlarged sectional `view of the compressor shown in Fig. 1, and Fig. 3 is a sectional view on the line 3-'3 of Fig. 2.

'Referring now to the drawing, in Fig. 1 I have shown a refrigerating machine including a casing casing i3 of the compressor I3, and is compressed and discharged through a connection I1 to an aircooled lcondenser I3 spaced from the casing Il and secured thereto on a plurality of radial fins' i3. The compressed refrigerant is cooled and liqueiledl within 4the condenser .i3 and ows through a connection 20 to a receiverA or float valve chamber 2l. 'I'he liquid refrigerant which collects in the'chamber 2i flows through a connection 22 to an evaporator 23 suspended by legs 10 24 below the top l i. The rate of flow of liquid refrigerant from the chamber 2i to the evapora- A tor 23 is regulated by a float valve or other suitable ilow controlling device. Liquid refrigerant within the evaporator 23v is vaporized upon the 15 absorption of heat from the compartment to be cooled, and the vaporized refrigerant collects in the headers 26 and 26 'which are in communication throughconduit 21 and is withdrawn vfrom the header 25 through 'a suction line 28 and re- 20 5. in mounted on an insulated top u of a rem;`

erator cabinet, and within the casing i0 are arranged a motori! and a compressor I3 oi.I the rotary type resiliently supported within the casing` on .upper and lower helical springs l5 and I6. `Gaseous refrigerant is withdrawn from the turns to the casing I0. In order to lubricate the motor and compressor a body of oil 29 is maintained in the bottom of the casing I0 and is cir-` culated through the motor and compressor by an oil pump. Cooling of the motor and compressor .25 is facilitated by a fan 30 secured on the motor shaft and rotated thereby.

Referring now to Fig. 2 the motor i 2 comprises a stator 3i mounted on a frame i 2a anda rotor 32 arranged to drive a-shaft 33 whichl is 30 journaled in the frame |2a of the compressor.

The compressor I3 comprisesa cylinder block 34, a rotor 35 mounted on an eccentric portion 36 of the shaft 33 and arranged to rotate within a vcompression chamber 31 formed in the cylinder 35 block 34. A cylinder head 38 is secured by a plurality of bolts 33 which pass through the cyli nder block 34 and irmly secure the -block 34 and the head 33 to the motor frame |2a, the lower end the rotor moves eccentrically within the chamber 31 the crescent-shaped space will likewise rotate about the chamber.' In order to utilize the movement of the rotor 35 to compress gas within the chamber 31 I provide a blade 40 slidably mounted t within a slot 4i in the block 34 at one side of the chamber 31 and extendingbetween the upper and lower cylinder heads of the compressor. The blade 4 3 is arranged to be Dressed into contact with the rotor so that the crescent-shaped space between the rotor and the cylinder block will be divided into intake and compression portions, except when the rotor 35 is in the position nearest the slot 4| as shown in liig. 3. The fluid to be compressed is admitted tothe chamber 31 through an intake port 42 and, as the rotor 35 turns around in a clockwise direction from the position shown in Fig. 3, the gas is compressed between the line of contact between the rotor 35 and the walls of the chamber 31 and the blade 40, and as the gas is compressed it is forced out through an exhaust port 43 provided with a check valve 44, which is urged against the port 43 by a spring 45. The lcompressed gas is discharged through a connection 46 and enters the conduit l1 leading to the condenser I5.

" In order to lubricate the compressor I provide a gear type oil pump including a gear 41 mounted on a reduced portion 48 ofthe shaft 33, and a second gear 49 meshing with the gear 41 and rotating on a pin 50 mounted in'the head 36.

I Both of the gears rotate in a chamber in a pump block 5I. During operation of the motor oil is drawn through a strainer 52 and a connection 53 into the gear pump and is discharged through a passage 54 to a chamber 55 i'ormed within the rotor 35. The oil lls the chamber 55 and thoroughly lubricates and seals the bearing'suriaces of the compressor and yis discharged therefrom through a passage 56.

In accordance with my invention I provide a mechanism for retaining the blade of the rotary compressorv in a retracted position to prevent loading of the compressor during starting, and an arrangement whereby uid pressure developed by the operation of the compressor will iorce the blade into operating position when a predetermined speed of the motor hasbeen reached. In

the embodiment illustrated, I provide a helical tension spring 51 secured to the blade 40 and to van adjusting screw 58 to retain the blade 40 in a retracted position within the slot 4l. When the blade is retracted in this manner the space b etweenthe rotor and the cylinder block is no ,longer dividedfinto intake and compression portions and the gas within the space is not compressedf. 'I'he rotor then does no "work on the gas and the compressor is unloaded. yThe oil from the passage 56 enters a cylinder 59 and is discharged therefrom through a passage 60 and enters the slot 4| to the rear ot the blade 40.

When the compressor has attained a predetermined speed the pressure of oil supplied by the gear pump becomes suiliciently great to force the blade through the'slot 4| against the tension of the spring 51 into contact with the rotor 35 to load the compressor. 'I'he pressure necessary to force theblade 40 into contact with the rotor 35 may be varied by adjusting the screw 56 and the nut 56a threaded thereon. 'Ihe oil pressure will remain suiilcient throughout operation oi' the compressor to maintain 4the blade 40 under presf sure against the rotor 35. Should the oil pressages are placed in communication with the casing as soon as the pressure is suillcient to uncover the passage63, and thus release the pressure and discharge excess oil. As a result the pressure of oil supplied back of the blade 40 is limited, and 5 power supplied to the motor I2 is shut ofi the coxn- 1'0 pressor will slow down, and at a predetermined speed the oil pressure will be insufiicient to maintain the blade 40 in contact with the rotor 35 and the compressor will be unloaded. This unloading action is positive and prevents jarring 15 of the mechanism when the motor is stopped.

While I have described my invention as applied to a 'compression refrigerating machine, other applications will readily become apparent to those skilled inthe art, and I do not desire my 20 invention to be limited to the specific construetion shown and described, and I intend in the appended claims to coverall modifications which do not depart from, the spirit and scope of my invention.

What I claim as newand desire to secure by Letters Patent of the United States, isz-f I 1. A iluid compressor including a Vstationary member having a compression chamber therein and inlet and outlet ports communicating with 30 said chamber, a rotatable member arranged within Asaid compression chamber, means for driving said rotatable member, means including a blade slidabiy mounted in onefof vsaid members lfor compressing uid between said members. 4means for 35 retracting said blade and for retaining saidblade in a retracted position in said one member to unv load said compressor, and means depe'ndent upon the operation of said driving means and producing iluid pressure for moving said blade into con- 40 tact with the other of said members to load said compressor.

2. A iluid compressor including la stationary member having a compression chambertherein, and inlet and outlet ports communicating with said chamber, a rotatable member arranged withf `in said compression chamber, means ,for driving l said rotatable member, means including a blade slidabiy mounted in one of said members for compressing iluid in said chamber, means including a spring for retracting said blade and for retaining said blade in a retracted position in said one member to unload said compressor, and means depends ent upon the operation of said driving means and producing fluid pressure for moving said blade into contact with the other oi' said members to load said compressor.

3. A iiuid compressor including a stationary member having a compression chamber therein and inlet and outlet Vports communicating with said chamber, a rotatable member arranged within said compression chamber, means including a blade slidabiy mounted in one of said members for compressing fluid in said chamber, means including a spring i'or retracting said blade and 65 for retaining said blade in a retracted position in said one member to unload said compressor, means for supplying lubricant under pressure to said compressor, and means dependent upon the pressure of said lubrieantfor movingsaid blade into contact with the other of said members to -load said compressor.

acuosa? member having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means includinga blade slidably mounted in one of said members for compressing iluid in said chamber, means including a spring for retracting said blade and having a compression chamber therein and inlet.

and outlet. ports communicating with said chamber, a rotor arranged within said compression chamber, a motor for driving. said rotor. means including a blade slidably mounted in said cylinder block and movable into contact with said rotor 'for compressing iiuid in said chamber,

,means for retracting said blade and for retaining said blade 'in' a retractedv positionl within said block to unload said'compressor, means including a lubricantpump driven by said motor i'or supplying lubricant under pressure to said compressor, means utilizing said lubricant for forcing said blade against said rotor to load said compressor, and vmeans for limiting the maximum pressure of said lubricant. A

7. A iluid compressor including a stationary member having a compressionchamber therein s and inlet and outlet ports communicating with said chamber, a rotatable member arranged within said compression chamber, means including a blade slidably mounted in one of said members ior compressing duid between said members, 10

-means .for supplying lubricant under pressure to said compressor, means for retracting said blade and i'or retaining said blade in a retracted position in said one member to unload said -compressor, means utilizing the pressure of lubricant supplied to said compressor for moving said blade into contact with the other of said members to load said compressor, and means for limiting the maximum pressure of said lubricant utilized to load said compressor.

8. A iluid compressor including a cylinder block having a compression chamber therein and inlet and outlet ports communicating with said chamber, a rotor arranged within said compression chamber, means including a blade slidably 25 mounted in said block and movable into contact with said rotor for compressing fluid in said chamber, means ior retracting said blade and for retaining said blade in a retracted position within said block to unload said compressor," means re- 30 sponsive to the operation of said compressor for supplying lubricant under pressure to said compressor, means utilizing the pressure of lubricant supplied to said compressor for moving said blade into contact with said rotor to load said com-35.

pressor, and means for limiting the maximum pressure of said lubricant utilized to load said compressor. i

' Y RUSSELL W. AYRES. 

